With significant developments in laser technology and its application to ophthalmology, laser surgery has become the technique of choice for ophthalmic procedures, such as refractive surgery for correcting myopia, hyperopia, astigmatism, and so on, and cataract surgery for treating and/or removing a cataractic lens. Often, a surgeon may prefer a surgical laser beam over manual surgical tools like microkeratomes because the laser beam can be focused precisely on extremely small amounts of eye tissue, thereby enhancing accuracy and reliability of the procedure.
Laser eye surgery generally uses different types of laser beams, such as ultraviolet lasers, infrared lasers, and near infrared, ultra-short pulsed lasers for various procedures and indications. For example, in the commonly-known LASIK (Laser Assisted In Situ Keratomileusis) procedure, an ultra-short pulsed laser is used to cut a corneal flap to expose the corneal stroma for photoablation with an excimer laser that operates in the ultraviolet range. Non-ultraviolet, ultra-short pulsed lasers emit radiation with pulse durations as short as 10 femtoseconds and as long as 3 nanoseconds, and a wavelength between 300 nm and 3000 nm. Besides cutting corneal flaps, ultra-short pulsed laser systems can also be used to perform cataract-related surgical procedures, including opening cataract incisions, capsulotomy, as well as softening and/or breaking of the cataractous lens. They can further be used for lenticule extraction procedures for refractive correction. Examples of laser systems that provide ultra-short pulsed laser beams include Abbott Medical Optics Inc.'s iFS Advanced Femtosecond Laser System and CATALYS Precision Laser System.
Optics and lenses for laser systems are typically complex and expensive. Instead of using an expensive lens with a large radius, some laser systems use a beam delivery system to move a lens assembly near an eye to direct the laser beam to different areas of the eye for surgery with a desired small spot size, thereby reducing system cost. The mechanical system which moves the lens assembly must do so with very precise motion control (e.g., micron level accuracy) and at a relatively high rate of speed, and is typically quite heavy.
In addition, it is necessary to stabilize patient's eye during laser surgery in a predetermined position relative to the focal point of the laser beam. This is normally done by physically constraining eye movement during laser surgery by applying an eye docking assembly to the patient's eye prior to the surgery. The eye docking assembly is fixed to the laser surgery system on the one end, and fixes an applanating lens in a patient interface onto the patient's eye on the other end.
During eye surgery under such circumstances, system vibrations have to be maintained so that they are very low, or else any unbalanced vibrations will be applied to the eye. As noted above, however, in a system where a beam delivery system moves a lens assembly during the surgery, it is very difficult to eliminate vibrations. Furthermore, in the case of a loss of electrical power, it is possible that the weight of the beam delivery system may be transferred to the patient's eye.
Accordingly, it would be desirable to provide an arrangement and method whereby the eye of a patient during laser surgery may be maintained in a predetermined position relative to the focal point of a laser beam during laser surgery while reducing the loading imposed upon the eye by any vibrations or movement of the laser eye surgery equipment.